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Dell EMC Configuration Guide for the S4048T–ON System 9.14.2.4

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Configure IPv6 NH Automatically for IPv6 Prefix Advertised over IPv4 Neighbor

You can configure the system to pick the next hop IPv6 address dynamically for IPv6 prefix advertised over an IPv4 neighbor configured under IPv6 address family. If there is no IPv6 address configured on the local interface, the system uses the IPv4 mapped IPv6 address. If there are multiple IPv6 addresses configured on the interface, the system uses the lowest IPv6 address configured on that interface. If the configuration is already present and a new IPv6 address, which is lower than the lowest existing address, is assigned to one of the peer interfaces, that address is not used as the NH until you flap the interface manually.

Figure 1. Configure IPv6 NH to advertise IPv6 prefix over IPv4 neighbor
Illustration for configure IPv6 NH

To enable BGP to pick the next hop IPv6 address automatically for IPv6 prefix advertised over an IPv4 neighbor, use the following commands.

Enable the system to pick the next hop IPv6 address dynamically for IPv6 prefix advertised over an IPv4 neighbor.
ROUTER-BGP mode mode
neighbor {ip–address | peer-group-name} auto-local-address
Enter either the neighbor IP address or the name of the peer group.
NOTE If outbound policy is applied along with auto-local-address enabled, then policy takes precedence.

Example configuration of BGP to automatically pick IPv6 address automatically for IPv6 prefix advertised over an IPv4 neighbor

The following example configuration demonstrates how to configure BGP to automatically pick IPv6 address for IPv6 prefix advertised over an IPv4 neighbor.

Example configuration performed in R1

DellEMC# configure terminal
DellEMC(conf)# router bgp 655
DellEMC(conf-router_bgp)# neighbor 10.1.1.2 remote-as 20
DellEMC(conf-router_bgp)# neighbor 10.1.1.2 auto-local-address
DellEMC(conf-router_bgp)# neighbor 10.1.1.2 no shutdown
DellEMC(conf-router_bgp)# bgp router-id 1.1.1.1
DellEMC(conf-router_bgp)# address-family ipv6 unicast
DellEMC(conf-router_bgpv6_af)# neighbor 10.1.1.2 activate
DellECM(conf-router_bgpv6_af)# exit

Configuring the auto-local-address for a neighbor will dynamically pick the local BGP interface IPv6 address (2001::1/64) as a the next hop for all the updates over IPv4 neighbor configured under IPv6 address family. If the auto-local-address is not configured, the IPv4 mapped IPv6 address (10.1.1.1) as a next hop.

Following is the show running-config command output for the above configuration.

DellEMC# show running-config bgp
!
router bgp 655
 bgp router-id 1.1.1.1
 neighbor 10.1.1.2 remote-as 20
 neighbor 10.1.1.2 auto-local-address
 neighbor 10.1.1.2 no shutdown
 !
 address-family ipv6 unicast
  neighbor 10.1.1.2 activate
  exit-address-family
 !

Example configuration performed in R2

DellEMC# configure terminal
DellEMC(conf)# router bgp 20
DellEMC(conf-router_bgp)# neighbor 10.1.1.1 remote-as 655
DellEMC(conf-router_bgp)# neighbor 10.1.1.1 no shutdown
 DellEMC(conf-router_bgp)# address-family ipv6 unicast
DellEMC(conf-router_bgpv6_af)# neighbor 10.1.1.1 activate
DellECM(conf-router_bgpv6_af)# exit

Following is the show running-config command output for the above configuration.

DellEMC# show running-config bgp
!
router bgp 20
neighbor 10.1.1.1 remote-as 655
neighbor 10.1.1.1 no shutdown
!
address-family ipv6 unicast
  neighbor 10.1.1.1 activate
  exit-address-family
!

Following is the show ip bgp ipv6 unicast command output for the above configuration.

DellEMC# show ip bgp ipv6 unicast
BGP local RIB : Routes to be Added 0, Replaced 0, Withdrawn 0
BGP local router ID is 1.1.1.1
Status codes: s suppressed, S stale, d dampened, h history, * valid, > best
Path source: I - internal, a - aggregate, c - confed-external, r - redistributed
             n - network,  D - denied,  S - stale
Origin codes: i - IGP, e - EGP, ? - incomplete

    Network            Next Hop            Metric     LocPrf Weight Path
*>  2001::/64          2001::1                  0                 0 655 ?
*>  3001::/64          3001::1                  0                 0 655 ?
*>  4001::/64          3001::1                  0                 0 655 ?
*>  5001::/64          3001::1                  0                 0 655 ?

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